The distribution and location of the symbiont Lagenophrys aselli on the freshwater isopod Asellus aquaticus

1. The distribution and location of the ciliated protozoan Lagenophrys aselli on the freshwater isopod Asellus aquaticus were studied in relation to water flow over the third pleopod surface. 2. At low densities L. aselli had a significant preference for the anterior centre of the pleopod; however, at the highest densities this preference was no longer significant. The distribution ranged from closer than random at low densities to further than random at the highest densities, and may have been a product of feeding and reproduction of L. aselli as well as the short intermoult period of the host. 3. An individual L. aselli has an effective area of both the lorica and the ciliated feeding disc. The ciliated feeding disc, when extended, may contribute to the presence of a small anterior–posterior gap being left between individuals.     

Evolution of the C<Subscript>4</Subscript> phosphoenolpyruvate carboxylase promoter of the C<Subscript>4</Subscript> species <Emphasis Type="Italic">Flaveria trinervia</Emphasis>: the role of the proximal promoter region

Background  

The key enzymes of photosynthetic carbon assimilation in C₄ plants have evolved independently several times from C₃ isoforms that were present in the C₃ ancestral species. The C₄ isoform of phosphoenolpyruvate carboxylase (PEPC), the primary CO₂-fixing enzyme of the C₄ cycle, is specifically expressed at high levels in mesophyll cells of the leaves of C₄ species. We are interested in understanding the molecular changes that are responsible for the evolution of this C₄-characteristic PEPC expression pattern, and we are using the genus Flaveria (Asteraceae) as a model system. It is known that cis-regulatory sequences for mesophyll-specific expression of the ppcA1 gene of F. trinervia (C₄) are located within a distal promoter region (DR).     

The changes in the predatory behavior of the microturbellarian <Emphasis Type="Italic">Stenostomum sphagnetorum</Emphasis> on two species of toxin-secreting ciliates of the genus <Emphasis Type="Italic">Spirostomum</Emphasis>

It is known that the microturbellarian Stenostomum sphagnetorum, a common ciliate predator, is very sensitive against different types of toxins produced by other ciliates for chemical defense, and consequently, it is not able to capture and ingests these ciliates. In particular, when the predator tries to attack one of these toxin-secreting ciliates, it is forced to regurgitate the captured prey in response to the toxin discharged from the ciliates. In this study it is shown that after repeated attacks by S. sphagnetorum against two species of toxic ciliates (Spirostomum ambiguum and Spirostomum teres), the predator acquires a behavior of prey selection that leads to the exclusion of these ciliates among the possible prey and to the distinction between edible and inedible (toxic) ciliates. This learned behavior, which is maintained for days, is lost only after the asexual reproduction of the microturbellarian. In addition, S. sphagnetorum learns to recognize and avoid specimens of S. ambiguum and S. teres artificially deprived of their toxins, strongly suggesting that the toxins are not exclusively associated in the prey recognition of the microturbellarian.     

Study of the enhancer-blocking activities of new boundaries in the <Emphasis Type="Italic">bithorax</Emphasis> complex of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

It was shown earlier that the Mcp, Fab-7, and Fab-8 boundaries of the bithorax complex contain insulators that effectively block the enhancers of the yellow and white genes. Other boundaries have not been studied so far. The recent mapping of binding sites for the insulator protein dCTCF in the regulatory regions of the bithorax complex genes permitted the Fab-3, Fab-4, and Fab-6 boundaries to be localized. Here, we showed that, despite the presence of dCTCF-binding sites, fragments of the Fab-3, Fab-4, and Fab-6 boundaries do not exhibit the properties of insulators in the model system with the yellow and white genes. Moreover, in some regions of the genome the Fab-4 and Fab-6 boundaries display the properties of silencers.     

Homology modeling of the transmembrane domain of the GABA<Subscript>A</Subscript> receptor

The permeability of ion channels for ions and substances that bind inside the pore depends on the cross-sectional area of the pore. We have constructed models of the closed, open, and desensitized α₁β₂γ₂ GABA_A receptor on the basis of known structures of both prokaryotic and eukaryotic ligand-gated channels. We employed Monte Carlo energy minimization to optimize the model structures. We have found significant pore constrictions, whose diameter depends on the functional state of the receptor in the cytoplasmic, middle, and extracellular parts of the pore-forming M2 segments. It is known that the constrictions in the middle (the 9' ring of residues) and cytoplasmic (the 2' ring of residues) parts of the M2 helices form the activation and desensitization gates of the GABA_A receptor. Our computations predict that the constriction in the extracellular part of the M2 helices (the 20' ring of residues) may also serve as a gate in the GABA_A receptor, whose physiological role is still unclear. Our results imply that the structures of a number of prokaryotic and eukaryotic ligand-gated channels that have been found in bacteria and lower organisms can be used for homology modeling of the pore region of the human GABA_A receptor.     

Distribution of the ticks <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> and <Emphasis Type="Italic">Ixodes pavlovskyi</Emphasis> on the boundary of the forest and forest-steppe zones in the Ob region

Surveys of ixodoid ticks were performed in Novosibirsk Province (Novosibirsk and Toguchin Districts) and in the vicinity of Akademgorodok (Novosibirsk) in 2009–2010. The abundance and distribution of ticks were assessed in 8 types of habitats. Ixodes persulcatus (Schulze, 1930) was collected by flagging in Novosibirsk and Toguchin Districts, with the highest densities of 19 ind./km being observed in habitats with small-leaved trees. Three species of ticks: Ixodes persulcatus, I. pavlovskyi (subspecies I. pavlovskyi occidentalis Filip. et Pan., 1998), and Dermacentor reticulatus (Fabricius, 1794) were recorded in a recreational forest of Akademgorodok. A high abundance (22 ind./km) of I. pavlovskyi was observed in pine forests subjected to considerable recreational load. The abundance of I. persulcatus was the highest in aspen-birch and birch-aspen forests. D. reticulatus was captured in pine forests and fallow lands, its abundance varying from 0.2 to 2 ind./km.     

Conservation of <Emphasis Type="Italic">ParaHox</Emphasis> genes' function in patterning of the digestive tract of the marine gastropod <Emphasis Type="Italic">Gibbula varia</Emphasis>

Background  

Presence of all three ParaHox genes has been described in deuterostomes and lophotrochozoans, but to date one of these three genes, Xlox has not been reported from any ecdysozoan taxa and both Xlox and Gsx are absent in nematodes. There is evidence that the ParaHox genes were ancestrally a single chromosomal cluster. Colinear expression of the ParaHox genes in anterior, middle, and posterior tissues of several species studied so far suggest that these genes may be responsible for axial patterning of the digestive tract. So far, there are no data on expression of these genes in molluscs.     

Effects of Bacillus thuringiensisδ-endotoxin-fed Helicoverpa armigera on the survival and development of the parasitoid Campoletis chlorideae

With the deployment of transgenic crops expressing δ‐endotoxins from Bacillus thuringiensis (Bt) for pest management, there is a need to generate information on the interaction of crop pests with their natural enemies that are important for regulation of pest populations. Therefore, we studied the effects of the Bt δ‐endotoxins Cry1Ab and Cry1Ac on the survival and development of the parasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) reared on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae fed on Bt toxin‐intoxicated artificial diet. The H. armigera larvae fed on artificial diet impregnated with Cry1Ab and Cry1Ac at LC₅₀ (effective concentration to kill 50% of the neonate H. armigera larvae) and ED₅₀ (effective concentration to cause a 50% reduction in larval weight) levels before and after parasitization resulted in a significant reduction in cocoon formation and adult emergence of C. chlorideae. Larval period of the parasitoid was prolonged by 2 days when fed on Bt‐intoxicated larvae. No adverse effects were observed on female fecundity. The observed effects appeared to be indirect in nature, because no Bt proteins were detected through enzyme‐linked immunosorbent assay in the C. chlorideae larvae, cocoons, or adults fed on Cry1Ab‐ or Cry1Ac‐treated H. armigera larvae. The effects of Bt toxin proteins on C. chlorideae were due to early mortality of H. armigera larvae, that is, before completion of parasitoid larval development.     

Vegetation of the aquatic and marshland habitats in the Orava region,including the first records of <Emphasis Type="Italic">Potametum alpini,Potametum zizii</Emphasis> and <Emphasis Type="Italic">Ranunculo-Juncetum bulbosi</Emphasis> in the territory of Slovakia

The vegetation of the aquatic and marshland habitats of the Orava region (north of Slovakia) was studied in 2009, using traditional phytosociological methods. Sixteen aquatic and eighteen marsh plant communities were described within 96 phytosociological relevés by using TWINSPAN with the application of the dominance principle. Three associations, Potametum alpini, Potametum zizii and Ranunculo-Juncetum bulbosi, were found as new communities for Slovakia. Myriophylletum verticillati, Potametum nodosi, Potametum graminei and Alisma gramineum community were recorded in the northernmost localities in Slovakia. Among marsh communities, Calletum palustris is very rare, both in the Orava region and in Slovakia as a whole. According to Ellenberg’s indicator values (EIV), moisture was evaluated as the main ecological gradient. Plant communities are ordered along the first Detrended Correspodence Analysis (DCA) axis in a typical hydroseries (Potametea → Lemnetea → Phragmition communis → Phalaridion arundinaceae, Oenanthion aquaticae and Sparganio-Glycerion → Magnocaricion elatae). The second DCA axis was most correlated with EIV for nutrients. Among the five directly measured ecological characteristics (temperature, pH and conductivity of water, water depth, and substrate type), conductivity of water (0.44, P < 0.01) and substrate type (0.32, P < 0.05) were the statistically significant variables explaining the variability along the first DCA axis.     

Origin of the plague microbe <Emphasis Type="Italic">Yersinia pestis</Emphasis>: Structure of the process of speciation

The origin and evolution of the plague microbe Yersinia pestis are considered in the context of propositions of modern Darwinism. It was shown that the plague pathogen diverged from the pseudotuberculous microbe Yersinia pseudotuberculosis O:1b in the mountain steppe landscapes of Central Asia in the Sartan: 22000-15000 years ago. Speciation occurred in the tarbagan (Marmota sibirica)-flea (Oropsylla silantiewi) parasitic system. The structure of the speciation process included six stages: isolation, genetic drift, enhancement of intrapopulational polymorphism, the beginning of pesticin synthesis (genetic conflict and emergence of hiatus), specialization (stabilization of characteristics), and adaptive irradiation (transformation of the monotypic species Y. pestis tarbagani into a polytypic species). The scenario opens up wide prospects for construction of the molecular phylogeny of the plague microbe Y. pestis and for investigation of the biochemical and molecular-genetic aspects of “Darwinian” evolution of pathogens from many other nature-focal infections.     

Origin of the Genus <Emphasis Type="Italic">Homo</Emphasis>

The origin of the genus Homo in Africa signals the beginning of the shift from increasingly bipedal apes to primitive, large-brained, stone tool-making, meat-eaters that traveled far and wide. This early part of the human genus is represented by three species: Homo habilis, Homo rudolfensis, and Homo erectus. H. habilis is known for retaining primitive features that link it to australopiths and for being the first stone tool makers. Little is known about H. rudolfensis except that it had a relatively large brain and large teeth compared to H. habilis and that it overlapped in time and space with other early Homo. Our understanding of the paleobiology and evolution of the larger-brained H. erectus is enhanced due to its rich fossil record. H. erectus was the first obligate, fully committed biped, and with a body adapted for modern striding locomotion, it was also the first in the human lineage to disperse outside of Africa. The early members of the genus Homo are the first to tip the scale from the more apish side of our evolutionary history toward the more human one.     

Theoretical assessment of oscillations in the concentrations of P<Stack><Subscript>700</Subscript><Superscript>+</Superscript></Stack> and intermediates of the Calvin-Benson cycle

A theoretically obtained oscillatory mode of photosynthesis caused by long-wave illumination is discussed. Periodical variations in the operation of photosystem (PS) I, the electron transport chain, and the Calvin-Benson cycle take place in this mode. The changes in PS II operation are not repetitive. Damped oscillations of P₇₀₀⁺ concentration and CO₂ assimilation rate are observed in the theoretical curves. The results of modeling are quite consistent with the P₇₀₀⁺ kinetics obtained earlier by measuring the induction of the PS I EPR signal in leaves at different temperatures.     

Biophysical mechanisms of physiological water exchange with the surroundings by the cells of the <Emphasis Type="Italic">Nitella translucens</Emphasis> and <Emphasis Type="Italic">Chara corallina</Emphasis> plants

In the present study, we discussed the biophysical mechanisms of stationary water exchange with the surroundings by the Nitella translucens and Chara corallina plants. It was postulated that these plants, which subsist under total immersion in a water medium, conduct water exchange within single cells individually. With the application of the equations of mechanistic formalism for membrane transport to our investigations (Kargol and Kargol 2000, Kargol 2001, Kargol 2002, Kargol and Kargol 2003, 2003*), it was demonstrated that individual cells of these plants can simultaneously absorb and remove considerable amounts of water at constant cell volume, i.e. under stationary conditions. Water absorption is osmosis-driven, and its removal is effected by the cell turgor pressure.     

Specialised placement of morphs within the gall of the social aphid <Emphasis Type="Italic">Pemphigus spyrothecae</Emphasis>

Background  

The strategic placement and aggregation of certain castes within the nests of eusocial insects such as bees and ants results in complex colonies that enjoy increased fitness through improved efficiency of social tasks. To examine if this advanced social phenomenon might apply to social aphids, the location of the numerous morphs within the nests (plant galls) of the aphid species Pemphigus spyrothecae was examined.     

Chemical constituents of the plants of the genus <Emphasis Type="Italic">Cleistanthus</Emphasis> and their biological activity

Chemical examinations of Cleistanthus collinus Roxb., a poisonous tree from India, and Cleistanthus patulus Muell. Arg. have resulted in isolation of a number of arylnaphthalide lignans and their glycosides as well as some furofuranoid lignans. While Cleistanthus gracilis Hook. f. from Thailand afforded an unusual glucoside of 2-β-hydroxy-8-azabicyclo-(5,0,2)-4β, 9β-epoxynona-5,7-diene, C. schlechteri from South Africa was the first reported source of the pimarane diterpenes. Cleistanthin A and cleistanthin B, diphyllin glycosides isolated from C. collinus were reported to exhibit cytotoxicity on several cancer cell lines. Cleistanthin A was found to cause DNA strand breaks and induce apoptosis in cultured cells while cleistanthin B caused G1 arrest and induced apoptosis in mammalian cells.